Surface-modified polycrystalline diamond and processing method thereof

ABSTRACT

A surface-modified polycrystalline diamond and a processing method thereof are provided in the present disclosure. The polycrystalline diamond comprises a polycrystalline diamond body, holes are formed on the polycrystalline diamond body after a catalyst metal is removed, and the holes are embedded with a non-catalyst metal after the catalyst metal is removed therefrom. Thus, thermal damage and stress damage to the polycrystalline diamond during operations at a high temperature are eliminated, improving the thermal conductivity of the surface of the polycrystalline diamond, reducing the temperature of the area around the operating point of the polycrystalline diamond and, therefore, the service life of the polycrystalline diamond is prolonged.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of China Patent Application No. 201110050119.6, filed on Mar. 2, 2011, in the State Intellectual Property Office of the People's Republic of China, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF INVENTION

1. Field of the Invention

The present disclosure relates to improvement of properties of polycrystalline diamonds, and more particularly, to a surface-modified polycrystalline diamond and a processing method thereof.

2. Description of the Related Art

Polycrystalline diamond compacts (briefly called PDCs) are made from a diamond powder incorporating a certain amount of sintering aids therein and a cemented carbide substrate, which are assembled together and then sintered on a special diamond hydraulic press at an high temperature under an ultra-high pressure. A PDC is composed of a polycrystalline diamond layer and the cemented carbide substrate. Because the polycrystalline diamond layer has high hardness and good wear resistance and the substrate is excellent in toughness and weldability, the PDCs are widely applied in the fields of oil drilling, geological drilling, coal field exploitation, cutting, and so on.

When PDCs or integrated polycrystalline diamonds are manufactured, cobalt, nickel, or iron is usually used as the sintering aids to sinter the diamond powder at an high temperature under an ultra-high pressure. The most common catalyst metal is cobalt or an alloy thereof, and the common pressure for sintering at an high temperature under an ultra-high pressure is 4.5 GPa to 6 GPa. Under this condition, the aforesaid sintering aids need to be used so that the diamond particles can be directly sintered with each other to form a diamond-diamond (D-D) combination structure, thereby achieving a polycrystalline diamond layer having excellent properties. The microstructure of the polycrystalline diamond consists of a diamond phase having frameworks connected with each other and a dispersed islet-shaped metal phase.

After the diamond particles are sintered into the frameworks, the properties of the entire polycrystalline diamond totally depend on the combination of the diamond frameworks. The greater the diamond particles are combined with each other and the larger the combination area is, the better the strength and wear resistance of the polycrystalline diamond will be. The strength is substantially unrelated to the metal phase dispersed in interstices between the frameworks. On the contrary, existence of iron group metal phases is detrimental to the performance of the polycrystalline diamond, including causing thermal damage and stress damage to the performance of the polycrystalline diamond.

When the PDC operates as a tool, there is often very high operating temperature around the operating point where the PDC contacts with a work piece, and the temperature may be about 700° C. to 800° C., or even over 1000° C. at some points. As shown by researches, cobalt, nickel or iron, which is used as a catalyst metal for catalyzing transformation of graphite into the diamond under a high pressure, but it also catalyzes transformation of the diamond into graphite under the normal pressure. Consequently, the iron group metal phase in the PDC can degrade the wear resistance of the PDC to some extent depending on different high temperatures of operating points, thereby causing a thermal damage.

A thermal expansion coefficient of the diamond is only one tenth of cobalt. When the operating temperate is very high, the cobalt phase expands to an extent much greater than that of the diamond frameworks, thereby generating a thermal stress. After reaching a certain value, the thermal stress will destroy the diamond frameworks to cause cracks in the polycrystalline diamond, thereby leading to stress damage.

Accordingly, the structure of the existing polycrystalline diamond body and the method of processing the polycrystalline diamond body in the art need further improvement and enhancement.

SUMMARY OF THE INVENTION

In view of the shortcomings of the prior art, an objective of the present disclosure is to provide a surface-modified polycrystalline diamond and a processing method thereof, in which a catalyst metal is removed from a polycrystalline diamond body to form holes and a non-catalyst metal having a high thermal conductivity is embedded into the holes. Thus, thermal damage and stress damage to the polycrystalline diamond body during operations at a high temperature are eliminated.

To achieve the aforesaid objective, the present disclosure provides the following technical solutions:

A surface-modified polycrystalline diamond, which comprises a polycrystalline diamond body, wherein holes are formed on the polycrystalline diamond body after a catalyst metal is removed, and the holes are embedded with a non-catalyst metal.

The surface-modified polycrystalline diamond, wherein the non-catalyst metal is one of copper, silver, aluminum, and alloys thereof.

The surface-modified polycrystalline diamond, wherein each of the holes has a depth of 0.1 mm to 1 mm.

The present disclosure further provides a method of processing a surface-modified polycrystalline diamond, which comprises the following steps of:

removing the catalyst metal from a surface of the polycrystalline diamond body and forming holes in the surface of the polycrystalline diamond body; and

embedding the non-catalyst metal into the holes.

The method of processing a surface-modified polycrystalline diamond, wherein the steps of removing the catalyst metal from the surface of the polycrystalline diamond body and forming the holes in the surface of the polycrystalline diamond body comprise:

boiling the polycrystalline diamond body in an aqua regia for 20 to 60 hours; and

taking the polycrystalline diamond body out of the aqua regia and rinsing the polycrystalline diamond body until the polycrystalline diamond body becomes neutral.

The method of processing a surface-modified polycrystalline diamond, wherein the steps of embedding the non-catalyst metal into the holes comprise:

putting a copper wheel rotating at a rotating speed of 1400 revolutions per second (rps) into contact with the surface of the polycrystalline diamond body; and

feeding the copper wheel at 0.1 mm to 0.4 mm for strong friction such that the surface of the polycrystalline diamond body is covered in copper.

The method of processing a surface-modified polycrystalline diamond, wherein the polycrystalline diamond body is boiled in the aqua regia for 10 to 110 hours; and the polycrystalline diamond body is taken out of the aqua regia and rinsed until the polycrystalline diamond body becomes neutral.

The method of processing a surface-modified polycrystalline diamond, wherein the step of embedding the non-catalyst metal into the holes comprises: placing the polycrystalline diamond body into a copper mould for electrodeposition, with the mould being used as a cathode, a copper sulfate solution being used as an electrolyte, and a pure copper plate being used as an anode.

The method of processing a surface-modified polycrystalline diamond, wherein the non-catalyst metal is one of copper, silver aluminum, and alloys thereof.

The method of processing a surface-modified polycrystalline diamond, wherein each of the holes has a depth of 0.1 mm to 1 mm.

According to the surface-modified polycrystalline diamond and the processing method thereof provided in the present disclosure, the catalyst metal is removed from the polycrystalline diamond body, and the non-catalyst metal is embedded into the holes formed in the surface of the polycrystalline diamond after the catalyst metal is removed. Thus, thermal damage and stress damage to the polycrystalline diamond during operations at a high temperature are eliminated and, therefore, the service life of the polycrystalline diamond is prolonged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural view of a polycrystalline diamond according to an embodiment of the present disclosure;

FIG. 2 is a schematic structural view of the polycrystalline diamond according to an embodiment of the present disclosure after a catalyst metal is removed therefrom; and

FIG. 3 is a flowchart diagram of a method of processing the polycrystalline diamond according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure provides a surface-modified polycrystalline diamond and a processing method thereof. To make the objectives, technical solutions, and efficacies of the present disclosure clearer, the present disclosure will be further described herein below with reference to the attached drawings and embodiments thereof. It shall be understood that, the embodiments described herein are only intended to illustrate but not to limit the present disclosure.

Referring to FIG. 1 and FIG. 2, a surface-modified polycrystalline diamond according to an embodiment of the present disclosure comprises a polycrystalline diamond body 11 installed on a cemented carbide matrix 21. A plurality of holes 111 are formed on the polycrystalline diamond body 11 after a catalyst metal is removed therefrom, and the holes 111 are embedded with a non-catalyst metal.

The catalyst metal is one of iron, cobalt, and nickel, and the non-catalyst metal is one of copper, silver, aluminum, and alloys thereof. Each of the holes 111 preferably has a depth of 0.1 mm to 1 mm; that is, only the catalyst metal at the depth of 0.1 mm to 1 mm from a surface of the polycrystalline diamond body 11 is removed in the present disclosure. According to the present disclosure, the holes 111 are formed in the surface of the polycrystalline diamond body 11 after the iron, cobalt, or nickel has been removed; and then the copper, silver, or aluminum has been embedded into the holes 111. In this way, the heat resistance of the polycrystalline diamond is improved and, thus, the service life of the polycrystalline diamond is prolonged.

None of copper, silver, and aluminum is a catalyst metal of the synthetic diamond and cannot catalyze reverse transformation of the diamond into graphite. Copper has a thermal conductivity of 397 W/mK, silver has a thermal conductivity of 429 W/mK, aluminum has a thermal conductivity of 217 W/mK, and cobalt has a thermal conductivity of only 96 W/mK. Replacing cobalt, nickel, or iron with one of copper, silver, aluminum, or an alloy thereof is beneficial to the improvement of the overall thermal conductivity of the polycrystalline diamond, and this makes it easier to dissipate heat from the surface of the polycrystalline diamond body 11 so that the operating temperature at the operating point of the polycrystalline diamond body 11 can be reduced.

In this embodiment, although the thermal conductivity of silver is slightly higher than that of copper, silver is much more expensive than copper. Therefore, copper or an alloy thereof is preferably used in the present disclosure to replace cobalt. Another choice is to use aluminum or an alloy thereof. Specifically, aluminum has a low melting point, so it is easier to embed aluminum into the holes 111; and additionally, at the operating point under a temperature above 700° C., the molten aluminum will overflow from the surface, thereby achieving the purpose of heat dissipation through “sweating”. Therefore, in this embodiment of the present disclosure, the non-catalyst metal having a high thermal conductivity is adopted to replace cobalt, nickel, and iron so as to eliminate thermal damage and stress damage to the polycrystalline diamond.

Correspondingly, an embodiment of the present disclosure further provides a method of processing a surface-modified polycrystalline diamond. Referring to FIG. 3, the processing method comprises the following steps of:

S110: coating an anticorrosion paint on the cemented carbide matrix of the polycrystalline diamond compact (PDC);

S210: removing a catalyst metal from a surface of the polycrystalline diamond body and forming holes in the surface the polycrystalline diamond body;

S310: embedding the non-catalyst metal into the holes; and

S410: sanding the surface of the polycrystalline diamond body by using an abrasive paper or an abrasive cloth so as to remove a redundant part of the non-catalyst metal from the surface of the polycrystalline diamond body.

In the step S210, the catalyst metal is iron, cobalt, or nickel, which is corroded from the surface of the polycrystalline diamond body mainly by an acid boiling method; however, the diamond has strong acid and alkali resistance and, thus, will not change after being treated with an acid or an alkali. After the catalyst metal is removed from the surface of the polycrystalline diamond body, the microstructure of the polycrystalline diamond body comprises a single diamond phase and dispersed holes.

In the step S310, the non-catalyst metal is one of copper, silver, aluminum, and alloys thereof. Copper, silver, or aluminum is only filled in the holes that are formed after the iron, cobalt, or nickel has been removed, and is particularly flexible and is only located on the surface. Therefore, there can be very small thermal stress generated due to a difference between a thermal expansion coefficient of copper, silver or aluminum and that of the diamond during operations at a high temperature, thereby eliminating thermal damage and stress damage.

The step S410 is optional, and may be executed by using a mechanical polishing method to polish the polycrystalline diamond until the surface thereof is exposed. In this case, it can be observed by means of a microscope that the microscopic holes in the surface of the polycrystalline diamond body have been filled by copper, silver, or aluminum. In practical implementations, a surface grinder of model M7132 may be adopted, in which a 240/270 fine diamond grinding wheel is slowly fed to grind off the surface of the polycrystalline diamond body by a thickness of about 0.01 mm, thereby grinding the surface into a polished surface. If there is no requirement on the appearance of the polycrystalline diamond body and the focus of attention is on the use and effect of the polycrystalline diamond body, then it is advantageous to maintain the copper layer on the surface of the polycrystalline diamond body.

As shown by researches, the larger the depth in the surface of the polycrystalline diamond body by which cobalt is removed and copper is filled is, the better the effect of the polycrystalline diamond body in practical applications will be and, thus, the longer the service life of the polycrystalline diamond will become. However, in case the depth by which cobalt is removed is over 0.5 mm, both the speed of removing cobalt and that of filling copper will be remarkably reduced, and this will significantly increase the manufacturing cost. Accordingly, in this embodiment of the present disclosure, the depth by which the cobalt is removed is 0.1 mm to 1 mm, and preferably 0.3 mm to 0.5 mm.

Hereinafter, the method of processing the surface-modified polycrystalline diamond according to this embodiment of the present disclosure will be described in detail with reference to examples thereof.

Embodiment 1

First step: enclosing the cemented carbide matrix of the polycrystalline diamond body with an anticorrosion fixture;

second step: boiling the polycrystalline diamond body in an aqua regia for 20 to 60 hours, and removing cobalt from the surface of the polycrystalline diamond body to a depth of 0.3 mm to 0.4 mm;

third step: after the aqua regia is cooled, taking the polycrystalline diamond body out of the aqua regia and rinsing the polycrystalline diamond body until the polycrystalline diamond body becomes neutral;

fourth step: putting a copper wheel rotating at a speed of 1400 revolutions per second (rps) into contact with the surface of the polycrystalline diamond body;

fifth step: feeding the copper wheel at 0.1 mm to 0.4 mm for strong friction such that the surface of the polycrystalline diamond body is covered by copper; and sixth step: sanding the surface of the polycrystalline diamond body by using a common No. 180 abrasive cloth or abrasive paper to remove the redundant purplish red copper layer until the surface of the black polycrystalline diamond body layer is exposed.

In practical implementations, given that a red copper wheel is used as an abrasion wheel on a surface grinder, the copper wheel rotating at a speed of 1400 rps is put into contact with the surface of the polycrystalline diamond that has been treated with an acid, and then fed at 0.2 mm for strong friction until the entire surface of the polycrystalline diamond is covered by the copper layer.

Embodiment 2

First step: coating an anticorrosion paint on the cemented carbide matrix of the polycrystalline diamond body;

second step: boiling the polycrystalline diamond body in an aqua regia for 10 to 110 hours, and removing cobalt from the surface of the polycrystalline diamond body to a depth of 0.4 mm to 0.6 mm;

third step: taking the polycrystalline diamond body out of the aqua regia and rinsing the polycrystalline diamond body until the polycrystalline diamond body becomes neutral;

fourth step: placing the polycrystalline diamond body into a copper mould for electrodeposition, with the mould being used as a cathode, a copper sulfate solution being used as an electrolyte, and a pure copper plate being used as an anode; and fifth step: sanding the surface of the polycrystalline diamond body by using a common No. 180 abrasive cloth or abrasive paper to remove the redundant purplish red copper layer until the surface of the black polycrystalline diamond body layer is exposed.

In the process of plating copper in an electrodeposition device, the polycrystalline diamond body is placed into a copper mould for electrodeposition, with the mould being used as a cathode, a copper sulfate solution being used as an electrolyte, and a pure copper plate being used as an anode. The electrolyte consists of 250 g/L of copper sulfate (CuSO₄.5H₂O) and 0.1 g/L of polyethylene glycol solution. In practical implementations, after the polycrystalline diamond body is placed into the electrolyte, the electrolyte is supplied with a current of 10 A/dm and is stirred at a speed of 150 r/min for 20 hours of electrodeposition at normal room temperature (i.e., 25° C.).

Embodiment 3

This embodiment differs from the second embodiment only in that, copper is filled into the holes by using an electroless copper plating method in the fourth step, wherein the electroless copper plating is accomplished by reducing copper ions under the action of a reducing agent on a surface having a catalytically active material, so that a copper plated layer is formed in the surface of the polycrystalline diamond body, with the solution being a CuSO₄ solution or a CuCl₂ solution.

Embodiment 4

This embodiment differs from the second embodiment only in that, the copper is evaporated into vapor by using a vacuum evaporation method in the fourth step so that a copper film is plated in the surface of the polycrystalline diamond body.

According to the above descriptions, in the surface-modified polycrystalline diamond and the processing method thereof provided in the present disclosure, the catalyst metal is removed from the polycrystalline diamond body, and the non-catalyst metal is embedded into the holes that are formed in the surface of the polycrystalline diamond after the catalyst metal is removed. Thus, thermal damage and stress damage to the polycrystalline diamond during operations at a high temperature are eliminated and, therefore, the service life of the polycrystalline diamond is prolonged.

It can be understood that, for those skilled in the art, equivalents or modifications can be made on the basis of the technical solution and the inventive concept provided in the present disclosure, and any of these equivalents and modifications shall also fall within the scope of the present disclosure. 

1. A surface-modified polycrystalline diamond, comprising a polycrystalline diamond body, wherein holes are formed on the polycrystalline diamond body after a catalyst metal is removed therefrom, and the holes are embedded with a non-catalyst metal.
 2. The surface-modified polycrystalline diamond of claim 1, wherein the non-catalyst metal is one of copper, silver, aluminum, and alloys thereof.
 3. The surface-modified polycrystalline diamond of claim 1, wherein each of the holes has a depth of 0.1 mm to 1 mm.
 4. A method of processing the surface-modified polycrystalline diamond of claim 1, comprising the following steps of: removing the catalyst metal from a surface of the polycrystalline diamond body and forming holes in the surface of the polycrystalline diamond body; and embedding the non-catalyst metal into the holes.
 5. The method of processing the surface-modified polycrystalline diamond of claim 4, wherein the steps of removing the catalyst metal from the surface of the polycrystalline diamond body and forming the holes in the surface of the polycrystalline diamond body comprise: boiling the polycrystalline diamond body in an aqua regia for 20 to 60 hours; and taking the polycrystalline diamond body out of the aqua regia and rinsing the polycrystalline diamond body until the polycrystalline diamond body becomes neutral.
 6. The method of processing the surface-modified polycrystalline diamond of claim 5, wherein the steps of embedding the non-catalyst metal into the holes comprise: putting a copper wheel rotating at a speed of 1400 revolutions per second (rps) into contact with the surface of the polycrystalline diamond body; and feeding the copper wheel at 0.1 mm to 0.4 mm for strong friction such that the surface of the polycrystalline diamond body is covered in copper.
 7. The method of processing the surface-modified polycrystalline diamond of claim 4, wherein: boiling the polycrystalline diamond body in an aqua regia for 10 to 110 hours; and taking the polycrystalline diamond body out of the aqua regia and rinsing the polycrystalline diamond body until the polycrystalline diamond body becomes neutral.
 8. The method of processing the surface-modified polycrystalline diamond of claim 7, wherein the step of embedding the non-catalyst metal into the holes comprises: placing the polycrystalline diamond body into a copper mould for electrodeposition, with the mould being used as a cathode, a copper sulfate solution being used as an electrolyte, and a pure copper plate being used as an anode.
 9. The method of processing the surface-modified polycrystalline diamond of claim 4, wherein the non-catalyst metal is one of copper, silver, aluminum, and alloys thereof.
 10. The method of processing the surface-modified polycrystalline diamond of any of claim 4, wherein each of the holes has a depth of 0.1 mm to 1 mm.
 11. The method of processing the surface-modified polycrystalline diamond of any of claim 5, wherein each of the holes has a depth of 0.1 mm to 1 mm.
 12. The method of processing the surface-modified polycrystalline diamond of any of claim 6, wherein each of the holes has a depth of 0.1 mm to 1 mm.
 13. The method of processing the surface-modified polycrystalline diamond of any of claim 7, wherein each of the holes has a depth of 0.1 mm to 1 mm.
 14. The method of processing the surface-modified polycrystalline diamond of any of claim 8, wherein each of the holes has a depth of 0.1 mm to 1 mm. 